linux-kernel - Re: [PATCHv4 0/9] zsmalloc/zram: configurable zspage size

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Message-ID: <Y21+xp52OQYi/qjQ@google.com>
Date:   Thu, 10 Nov 2022 14:44:22 -0800
From:   Minchan Kim <minchan@...nel.org>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCHv4 0/9] zsmalloc/zram: configurable zspage size

On Mon, Oct 31, 2022 at 02:40:59PM +0900, Sergey Senozhatsky wrote:
> 	Hello,
> 
> 	Some use-cases and/or data patterns may benefit from
> larger zspages. Currently the limit on the number of physical
> pages that are linked into a zspage is hardcoded to 4. Higher
> limit changes key characteristics of a number of the size
> classes, improving compactness of the pool and redusing the
> amount of memory zsmalloc pool uses. More on this in 0002
> commit message.

Hi Sergey,

I think the idea that break of fixed subpages in zspage is
really good start to optimize further. However, I am worry
about introducing per-pool config this stage. How about
to introduce just one golden value for the zspage size?
order-3 or 4 in Kconfig with keeping default 2?

And then we make more efforts to have auto tune based on
the wasted memory and the number of size classes on the
fly. A good thing to be able to achieve is we have indirect
table(handle <-> zpage) so we could move the object anytime
so I think we could do better way in the end.